I was always taught that certain “unnatural relations” were forbidden even among married couples. Your answers to some recent questions contradict this teaching. Can you justify your position from the Bible?
The one passage in which some form of the phrase “unnatural relations”appears is Romans 1:26-27.
Even their women exchanged natural relations for unnatural ones. In the same way the men also abandoned natural relations with women and were inflamed with lust for one another. Men committed indecent acts with other men, and received in themselves the due penalty for their perversion.
When Paul said women exchanged natural relations for unnatural ones, he was referring to women who abandoned men as sex partners in favor of other women. We know this because in the next sentence Paul said men also abandoned natural relations with women and committed indecent acts with other men. His point here was that heterosexual sex is natural, but homosexual sex is unnatural. The idea that certain sex acts are forbidden even between a husband and wife can not be supported in Scripture.